CIS 141 LectureStorage Hardware (saving data/information)
Thad CrewsWestern Kentucky University
SAVING INFORMATIONSTORAGE HARDWARE
(Remember: Digital vs. Analog)
•Digital systems have discrete values 1 / 2 / 3 / 4 / 5On / Off
• Digital with two states is called Binary
•Analog systems have continuous data values
(Remember: Bits and Bytes)
•A bit (e.g., “binary digit”) is a single one (1) or zero (0).
•Eight bits is a byte – the standard grouping in digital electronics
•1’s and 0’s can be used to represent:• Numbers• Letters• Sounds• Images• Videos
INPUT PROCESS• CPU• Memory
OUTPUT
Input – Process – Output
INPUT PROCESS• CPU• Memory
OUTPUT
Storage
This memory is volatile which means it requires electrical power to hold its value.
STORAGE
INPUT PROCESS• CPU• Memory
OUTPUT
Storage
• Hard Disk (magnetic)• CD/DVD/BD (optical)• USB Flash (solid
state)
“RAM”“Memory”“Main Memory”
“Secondary Memory”“Storage”
Main Memory vs. Storage Memory is volatile — holds data and instructions temporarily
Storage is nonvolatile — contents retained when power is off
So why not use “Storage” hardware for “Main Memory”?
Memory/Storage HierarchyCPU
Cache (L1, L2)
RAM (main memory)
Solid State (Flash) Storage
Magnetic Storage
Optical Storage
Faster Data Transfer & More Expensive
Slower DataTransfer &Less Expensive
Solid State Storage (Storage 1 of 3)
•Flash memory resides on a chip (e.g., solid state; no moving parts; like RAM.) However, flash memory is nonvolatile so it retains its information when it is “unplugged.”
A single 8GB USB/thumb/flash drive stores as much data as 1,000+ CDs
Mini Memory Card
Magnetic Storage (Storage 2 of 3)
•A hard disk is the most common magnetic storage media, consisting of several inflexible platters covered with magnetic material enclosed in an airtight, sealed case.
•Hard drive platters spin at a rate of ~8000 RPM.
The read/write head
Hard Disk
•A head crash occurs when the read/write head touches the platter surface.
Do NOT shake your machine while your hard drive is spinning.
Clearance between head and platter is approximately two-millionths of an inch
Hard Disks
•A Redundant Array of Independent Disks (RAID) connects multiple disks into a single unit to achieve high levels of storage reliability.
Older magnetic storage media
•Floppy disks•Tape drives
Solid State Drive vs. Hard Disk Drive
Your next computer may have a solid state drive (SSD) instead of a hard drive.• SSD Advantages:
• Faster (no spin start up, no moving head seek)
• Silent operation due to lack of moving parts
• Low power consumption• Generate little heat• Low failure rate
• SSD Disadvantages• More expensive per gigabyte• Great difference between write
speed and read speed (may cause problems)
SSD (Solid State Disks) Many competing standards
Optical Media Storage (Storage 3 of 3)
•CD, DVD, Blu-laser Disc (BD) are all optical media that use a laser to read and write the data on the disc.
Note: Magnetic disks are spelled with a “K”, and optical discs are spelled with a “C”.
Optical DiscsHow does a laser read data on an optical disc?
laserdiode
laserdiode
prism prismlight-
sensingdiode
light-sensing
diode
0 1
lens lenspit land
disc label
Step 1.Laser diode shines a light beam towarddisc.
Step 2.If light strikesa pit, it scatters. If light strikes a land, it is reflected back toward diode.
Step 3.Reflected light is deflected to alight-sensing diode, which sends digital signals of 1 to computer. Absence of reflected light is read as digital signal of 0.
Optical Discs
•CD, DVD, Blu-laser Disc (BD)
1 CD = 486 Floppy Disks1 DVD = 3,263 Floppy Disks
1 BD = 17,361 Floppy Disks
Recent News Stories about Storage
•NSA Spy Center: • Read more here
•White House Shares $200 Million Big Data Plan: • Read more here
•60th Anniversary of Tape Storage:• Read more here
SUMMARY (Computer Hardware)Ch7
Ch6 Ch
7
Ch8
Quiz1
(Remember: Prefixes)• A byte is about the size it takes to store a letter of the alphabet.
• A kilobyte is about the storage you would need for a six-page paper.
• 1.44 megabytes: A floppy disk.
• 500 megabytes: CD-ROM
• 4.7 gigabytes: DVD Disc
• 25 gigabytes: Blu-Ray Disc
• 1 terabyte: All the X-ray films in a large technological hospital
• 10 terabytes: Printed collection of the U. S. Library of Congress
• 500 terabytes: All the information in all the books ever written
• 24 petabytes: Google’s daily processing
• 500 exabytes: The world’s total digital content (as of May 2009).
Prefix ScaleK (kilo) Thousand
M (mega) MillionG (giga) BillionT (tera) TrillionP (peta) QuadrillionE (exa) Quintillion
Z (zetta) SextillionY (yotta) Septillion
Big Picture (Computer Hardware)
Big Picture (Computer Hardware)